In the traditional bioprocess development, the operation mode changes from batch in screening to fed-batch in lab and production scale. The presented dialysis shake flask allows small-scale fed-batch cultivations by a diffusion driven nutrient release. It consists of a feed reservoir system which is filled with a highly concentrated nutrient solution. The nutrient diffuses through a dialysis membrane into the medium. Cultivations with Escherichia coli BL21 (DE3) pRhotHi-2-EcFbFP and Hansenula polymorpha RB11 pC10-FMD (PFMD-GFP) proved the feasibility of the concept. As positive effects of these small-scale fed-batch cultivations, enhanced (up to 1000fold) yields for catabolite repressed product formation, reduced overflow metabolism and diminished medium acidification were observed. The new dialysis fed-batch shake flask is characterised by a high flexibility regarding the attainable feed rates and the spectrum of feedable compounds. The feed rate can be adjusted in a broad range by simply adapting the diffusion parameters. Based on the working principle, the release of any desired compound is possible. The dialysis fed-batch shake flask allows the detailed investigation of strains and process conditions under operation mode similar to industrial production process. Combined with the Respiration Activity Monitoring System (RAMOS), it represents an effective screening tool for the first steps of bioprocess development.

► Parallel small-scale fed-batch cultivations by continuous diffusion driven nutrient release. ► Screening in fed-batch mode similar to conditions in production process possible. ► Feed rate can be adjusted in a broad range and any desired nutrient can be fed. ► Up to 1000fold increase of catabolite repressed production in fed-batch mode. ► In combination with Respiration Activity Monitoring System powerful screening tool.